attention part 2. early selection model (broadbent, 1958) inputdetectionrecognition fi l t e r only...
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Attention
• Part 2
Early Selection Model (Broadbent, 1958)
input detection recognition
FILTER
Only information that passed the filter received further analysis (e.g. meaning).
Late Selection Theory(Deutsch & Deutsch, Norman)
input detection recognition
FILTER
Early Attenuation Model (Treisman)
input detection recognition
FILTER
Lab: Feature Search
Parallel processing of simple visual features (e.g., color).
Typical Results for “Feature Search”
# of items in display
6 10 20 30
ReactionTime(msec)
“Yes”
“No”
Conjunction Search
• Combination of features (e.g., red AND horizontal)
• Spatial arrangements of features (e.g. black above white)
When targets are defined by:
Lab: Conjunction Search
‘Find the blue square’
Lab: Conjunction Search
Treisman’s Results for “Conjunction Search”
# of items in display
2 4 6 10 20 30
ReactionTime(msec)
“Yes”
“No”
Lab: Voluntary Cueing
Valid Trials70%
Invalid Trials15%
Neutral Trials15%
Voluntary Cueing
250
270
290
310
330
350
Valid Neutral Invalid
• Same result for short and long cue-to-target delays (short ‘green’, long ‘blue’)
Lab: Automatic Cueing
Cued Trials??%
+
Miscued Trials
+
Neutral Trials
+
Automatic Cueing
250
270
290
310
330
350
Cued Neutral Invalid
• For short cue-to-target delay (‘green’), same result as for voluntary cueing (validly cued faster than invalidly cued)
• For long cue-target delays, the reverse pattern (inhibition of return)
+ +
Neurological Deficits in Visuo-spatial attention
• Hemi-spatial Neglect• lesion in right temporo-parietal junction
• Inability to – attend to the left side of visual space, and thus to– be aware of visual stimulus in the left visual field– Represent spatial relations.
Line-bisection task
RightLeft
LVF RVF
Righthemisphere
Lefthemisphere
LVF RVF
To study the neural substrate of visuo-Spatial Attention, we need
• A patient group: – Hemispatial neglect
• A simple method: – Spatial Cueing
• A cognitive theory: – Posner’s three stage model
• Disengage: – stop attending to what is currently being attended
• Move: – refocus spotlight on new location
• Engage: – begin attending to new stimulus
Spatial Cueing
Cued Trials
+
Miscued Trials
+
Retina
LGN
V1
V4 ParietalCortex
InferotemporalCortex
(Relay Station)
(Detects Edges)
(Color,Form)
(Shape,Object Recognition)
(Location,How to reach oract upon)
Which part of the brain is the source of attention?Where does attention have its effects?
time
Memory/Attention Task(fMRI / ERP)
Regions of Interest
RVF LVF
Stim 1 Stim 2
Single-Unit Recording
“spike” = single neuron’s action potential
(Macaque monkey)
SignalAnalysis
Receptive Field
Attention Effects inSingle Neuron Responses
100 msec
Frequencyofspikes
Attended bar
Unattended bar
(Robert Desimone, NIH)
Retina
LGN
V1
V4 ParietalCortex
InferotemporalCortex
(Relay Station)
(Detects Edges)
(Color,Form)
(Shape,Object Recognition)
(Location,How to reach oract upon)
AttentionEffectsHere
NoAttentionEffectsHere
Early visual processing IS affected by selective attention.
This is a challenge for a pure late selection model.
BUT, it does not mean that late selection is not occurring.
Conclusions from Neuroscientific Evidence:
Automatic vs. Voluntary Priming
+ AA
Warningsignal
Testsignal
neutral
(Posner & Snyder, 1975)
S KK15%
P PP
S KK
G GG15%
70%
“No need to think of P”
Automatic Priming
“think of P! yeah baby!”
Automatic Priming
Voluntary Priming
Often misleading
G GG70%
Often predictive
Differencebetweenexperimental and neutral conditions
faster
slower
15% primed
70%misled
70%primed
15%misled
Low validity(often misled)
High validity
P -> P
P ->G
P ->G
P ->P
Automatic Priming;Benefit without a cost
Voluntary PrimingBenefit with cost
Automatic vs Voluntary priming (part 2) Neely (1977)
• If you see a body part as a Prime, expect a building part as a target. For example, – Body -> door
• some pairs were semantically related, but unexpected– body -> heart
Priming Results
-80
-60
-40
-20
0
20
40
60
200 700 2000
• Blue: Expected pair– Body -> door– voluntary priming – Evolves with time
• Green: Related but unexpected– Body -> heart– automatic priming, followed
by a cost from voluntary priming Cue-target delay (ms)
Cos
t f
acil
itat
ion
(ms)
Question
• Predict pattern of performance when:– the delay between cue and target is very short, – the cue-target delay is longer
– For automatic priming– For voluntary priming
1. Selectivity: only aware of a subset of stimuli--selective attention.
2. Capacity Limitations: limited ability to handle different tasks or stimuli at once--divided attention.
3. Sustained mental effort: limited ability to engage in protracted thought, especially on the same subject--vigilance.
3 meanings of the word ‘Attention’
PSBONKG######
Attentional Blink
You will see a stream of letters rapidly presented in the center Group 1: memorize any vowels Group 2: memorize any vowels and red letters
Target 2
S
N
O
B Target 1 Encoding intoWorking Memory
Attentional Blink: Early or Late Selection?
• Instead of letters, use words.• An initial word establishes context (e.g., milk)• Target 2 is a word that is semantically related to
the context word or not (e.g., sugar, shoes)• When subjects fail to report T2, look at their brain
waves (ERPs) to assess whether the meaning of that target has been processed or not
• N 400 (ERP marker of semantic processing)
Spotlight metaphor
- metaphors are not right or wrong, they are useful or not…
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